In restaurants and bars which require frequent washing of glasses and other dishes it is important to ensure that the water used by the washer is hot enough for satisfactory cleansing. One method of obtaining this result is to incorporate a heater in the washer. The use of a heater, however, adds to the initial cost of the machine as well as to the cost of maintenance.
Another, and simpler method of having hot water at the beginning of each wash period is to start the water fill from a hot water supply and keep the drain open to exhaust the incoming water until such time as the incoming water becomes hot, following which the drain may be closed manually and the washing operation started. If the water supply is some distance away from the washer, it may take a minute or so for the water to become sufficiently hot. This method, therefore, requires the time and attention of the operator but there is no assurance that the operator will follow the recommended procedure. To avoid the inconvenience to an operator of having to monitor the incoming water temperature, it is therefore desirable to control the washer automatically with respect to the fill water temperature.